The present invention relates generally to pharmaceutical tablets and more particularly to a tablet containing both an antacid ingredient and an antigas ingredient consisting of simethicone.
Simethicone is described in the NATIONAL FORMULARY, 14th Edition, American Pharmaceutical Association, Washington, D.C., 1975, at page 648, as a mixture of not less than 93% and not more than 99% of dimethylpolysiloxane and not less than 4% and not more than 4.5% of silicon dioxide. Other characteristics of simethicone are described in the aforementioned publication at the page indicated, and that description is incorporated herein by reference. Dimethylpolysiloxane is sometimes referred to as polysiloxane or organopolysiloxane.
Rider U.S. Pat. No. 3,422,189 discloses a pharmaceutical tablet containing both an antacid ingredient and an anti-gas ingredient consisting of simethicone (called "Anti-foaming agent" therein), and the description of said Rider patent is incorporated herein by reference. As disclosed in the prior art, simethicone is an anti-foaming agent, and it also has the property of relieving flatulency symptoms in the digestive tract of humans.
Another prior art patent which discloses the combination of antacid and organopolysiloxane is Feinstone U.S. Pat. No. Re. 25,205.
When simethicone is combined in a tablet with essentially only a lactose filler, the tablet remains relatively fast-acting flatulency-relieving and anti-foaming characteristics even after the tablet has had a long shelf life. However, the simethicone is mixed with antacid ingredients, such as magnesium hydroxide or aluminum hydroxide or both, the rapidity with which the simethicone performs its anti-foaming function decreases as the shelf-life of the combination antacid--simethicone tablet increases. A reduction in the rapidity of the anti-foaming effect is indicative of a reduction in the rapidity of the antiflatulency effect.
Yen U.S. Pat. No. 3,501,571 disclosed the adverse effect on the rapidity of the anti-foaming function of polysiloxane when the latter is intimately mixed with antacid in a non-layered tablet. Yen ascribes this adverse effect to the fact that the polysiloxane is absorbed by the antacid particles so that little, if any, polysiloxane is available for anti-foaming action until the antacid matrix breaks down. In contrast, other substances, according to Yen, adsorb polysiloxane and retain it on the surface of the adsorbing particle where the availability of the polysiloxane for immediate anti-foaming action is not dependent upon the breakdown of the carrier particle. Such substances include lactose, mannitol, sorbitol, sucrose and dextrose.
To combat the slow acting anti-foaming action arising when simethicone is mixed with antacids, commercial embodiments of antacid-simethicone tablets have been prepared as a multi-layered tablet in which the antacid ingredients are in one layer and the simethicone is in another layer also containing lactose, the simethicone-containing layer being separate and discrete from the layer containing the antacid ingredients. Although the simethicone in such a multi-layered tablet has a faster acting anti-foaming effect after a given shelf life than does the simethicone in a tablet in which both the simethicone and the antacid ingredients are intimately mixed together, the problem of slowed anti-foaming action is still present. In other words, the simethicone in such a multi-layer tablet still has slower acting anti-foaming characteristics after a given shelf life than does a simethicone-lactose tablet containing no antacid ingredients whatsoever.
Other prior art attempts to deal with this problem include McVean U.S. Pat. No. 3,767,794 and Buehler U.S. Pat. No. 4,127,650 which teach suspending or entraining microscopic particles of simethicone within a matrix of either sorbitol (McVean) or glycerol and corn syrup (Buehler), then mixing with antacid and tableting. In this form, the simethicone is insulated from the antacid in the same tablet. The drawback to each of these attempts is that little, if any, simethicone is available for anti-foaming action until the matrix, be it sorbitol or glycerol-corn syrup, breaks down; and such a tablet is relatively slow acting compared to a tablet in which the availability of simethicone does not depend upon the breakdown of a matrix.
Moreover, because there is no digestion in the stomach, but only in the intestines, the breakdown of the matrix in the stomach would be by dissolution, only, a relatively slow process; and it would be impossible for the matrix to pass out of the stomach before breakdown was complete, thereby depriving the stomach of the anti-foaming action of the simethicone in the undissolved part of the matrix passing out of the stomach.